Field of the Disclosure
The present application relates to an organic light emitting display device. More particularly, the present application relates to an organic light emitting display device adapted to enhance reliability of elements and reduce the number of mask procedures, and to a method of manufacturing the same.
Description of the Related Art
Recently, flat panel display devices are being developed for replacing cathode ray tube devices (CRTs), which are heavy and have large volume. The flat panel display devices include liquid crystal display (LCD) devices and organic light emitting display (OLED) devices.
OLED devices are self-luminous and do not need an additional light source, unlike LCD devices. As such, OLED devices are thinner, have lighter weight and superior color reproduction ranges when compared to LCD devices. In accordance therewith, the OLED device is being spotlighted as a next generation display device.
OLED devices are generally classified into a passive type and an active type.
The active type of OLED device includes thin film transistors opposite to pixels. As such, the active type OLED device has advantages of lower power consumption and superior definition compared to the passive type OLED device. Therefore, the active type OLED device is mainly used to implement a large-sized image display device.
A display panel of an ordinary OLED device includes sub-pixels arranged in a matrix shape. The sub-pixels can include red, green and blue sub-pixels. Alternatively, the sub-pixels can each include a white sub-pixel and a color conversion layer configured to convert white light of the white sub-pixel into one of red, green and blue lights. Also, the sub-pixels can be of the active type or the passive type. For example, the active type sub-pixel includes a switching transistor configured to transfer a data signal in response to a scan signal, a storage capacitor used to store a data voltage corresponding to the data signal, a driving transistor configured to generate a driving current corresponding to the data voltage, and an organic light emitting diode configured to emit light corresponding to the driving current. Thus, the active type OLED sub-pixel can be formed in a 2T1C (two transistors and one capacitor) structure including the switching transistor, the driving transistor, the capacitor and the organic light emitting diode. Alternatively, the active type sub-pixel can be formed in one of 3T1C, 4T2C and 5T2C structures and so on. Also, the sub-pixel can be formed in one of a top emission mode, a bottom emission mode and a dual emission mode based on a cross-sectional structure.
FIG. 1 is a cross-sectional view showing an etch stopper and a contact hole formed through the same mask procedure in a related art method of manufacturing of an OLED device;
Referring to FIG. 1, a switching transistor or a driving transistor is formed in a thin film transistor structure. Although they are not shown in the drawing, storage electrodes, a pixel electrode and pads are simultaneously formed when the thin film transistor is formed.
The procedure of forming an etch stopper 15 included in the thin film transistor will now be described.
A metal film is formed on a substrate of a transparent insulation material. A gate electrode 11 is formed by performing a mask procedure for the metal film. Also, a gate insulation film 12 is formed on the entire surface of the substrate 10 provided with the gate electrode 11.
Thereafter, a channel layer 14 corresponding to a semiconductor layer is formed on the gate insulation film opposite to the gate electrode 11, and an etch stopper 15 is formed on the channel layer 14. The etch stopper is used to protect the channel layer 14. Also, a contact hole Ck exposing a part of the gate electrode 11 is formed in the gate insulation film 12. In general, the etch stopper 15 and the contact hole Ck are formed through different mask procedures. However, in order to reduce the number of mask procedures, the related art manufacturing method for an OLED device enables the etch stopper 15 and the contact hole Ck to be simultaneously formed.
Also, it is necessary to perform a heat treatment process for the etch stopper 15. The heat treatment process can be performed for the etch stopper which is formed by depositing an insulation layer for the etch stopper 15 and patterning the insulation layer through the mask procedure. Alternatively, the heat treatment process can be performed for an insulation layer deposited for the etch stopper before the insulation layer is patterned into the etch stopper 15 through the mask procedure.
However, it is preferable to perform the heat treatment process for the etch stopper 15 which is completed through the mask procedure. In this instance, the element can obtain superior reliability as shown in FIGS. 4A and 4B.
In view of this point, the related art manufacturing method of the OLED device allows the heat treatment process to be performed for the completed etch stopper 15 as shown in FIG. 1B. However, a part of the gate electrode 11 exposed the contact hole Ck can be damaged due to the heat treatment process.
In other words, the etch stopper 15 is completed through an etching process and the heat treatment process. A part of the gate electrode 11 is externally exposed through the gate contact hole Ck. Due to this, the gate electrode 11 might be damaged during the etching process and the heat treatment process.
Although only the gate electrode 11 shown in the drawing is described, a storage electrode and gate and data pads are formed on the substrate 10 in the same layer as the gate electrode, such that they are partially exposed through respective contact holes. As such, the storage electrode and the gate and data pads can be damaged during the formation procedure of the etch stopper 15.
These damages result in reliability deterioration of the elements and quality deterioration of images.